Early endosomal maturation of MHC class II molecules independently of cysteine proteases and H-2DM

Major histocompatibility complex (MHC) class II molecules bind and present to CD4(+) T cells peptides derived from endocytosed antigens. Class II molecules associate in the endoplasmic reticulum with invariant chain (Ii), which (i) mediates the delivery of the class II–Ii complexes into the endocytic compartments where the antigenic peptides are generated; and (ii) blocks the peptide-binding site of the class II molecules until they reach their destination. Once there, Ii must be removed to allow peptide binding. The bulk of Ii–class II complexes reach late endocytic compartments where Ii is eliminated in a reaction in which the cysteine protease cathepsin S and the accessory molecule H–2DM play an essential role. Here, we here show that Ii is also eliminated in early endosomal compartments without the intervention of cysteine proteases or H–2DM. The Ii-free class II molecules generated by this alternative mechanism first bind high molecular weight polypeptides and then mature into peptide-loaded complexes

The Ergonomics of Wheelchair Configuration for Optimal Performance in the Wheelchair Court Sports

<p>Optimizing mobility performance in wheelchair court sports (basketball, rugby and tennis) is dependent on a combination of factors associated with the user, the wheelchair and the interfacing between the two. Substantial research has been attributed to the wheelchair athlete yet very little has focused on the role of the wheelchair and the wheelchair-user combination. This article aims to review relevant scientific literature that has investigated the effects of wheelchair configuration on aspects of mobility performance from an ergonomics perspective. Optimizing performance from an ergonomics perspective requires a multidisciplinary approach. This has resulted in laboratory-based investigations incorporating a combination of physiological and biomechanical analyses to assess the efficiency, health/safety and comfort of various wheelchair configurations. To a lesser extent, field-based testing has also been incorporated to determine the effects of wheelchair configuration on aspects of mobility performance specific to the wheelchair court sports. The available literature has demonstrated that areas of seat positioning, rear wheel camber, wheel size and hand-rim configurations can all influence the ergonomics of wheelchair performance. Certain configurations have been found to elevate the physiological demand of wheelchair propulsion, others have been associated with an increased risk of injury and some have demonstrated favourable performance on court. A consideration of all these factors is required to identify optimal wheelchair configurations. Unfortunately, a wide variety of different methodologies have immerged between studies, many of which are accompanied by limitations, thus making the identification of optimal configurations problematic. When investigating an area of wheelchair configuration, many studies have failed to adequately standardize other areas, which has prevented reliable cause and effect. relationships being established. In addition, a large number of studies have explored the effects of wheelchair configuration in either able-bodied populations or in daily life or racing wheelchairs. As such, the findings are not specific and transferable to athletes competing in the wheelchair court sports. This review presents evidence about the effects of wheelchair configuration on aspects of mobility performance specific to the wheelchair court sports to better inform athletes, coaches and manufacturers about the consequences of their selections. It also provides researchers with guidance on the design of future investigations into areas of wheelchair configuration, which are essential.</p>

Field-Based Physiological Testing of Wheelchair Athletes

This article is closed access.The volume of literature on field-based physiological testing of wheelchair sports, such as basketball, rugby and tennis, is considerably smaller when compared with that available for individuals and team athletes in able-bodied (AB) sports. In analogy to the AB literature, it is recognized that performance in wheelchair sports not only relies on fitness, but also sport-specific skills, experience and technical proficiency. However, in contrast to AB sports, two major components contribute towards ‘wheeled sports’ performance, which are the athlete and the wheelchair. It is the interaction of these two that enable wheelchair propulsion and the sporting movements required within a given sport. Like any other athlete, participants of wheelchair sports are looking for efficient ways to train and/or analyse their technique and fitness to improve their performance. Consequently, laboratory and/or field-based physiological monitoring tools used at regular intervals at key time points throughout the year must be considered to help with training evaluation. The present review examines methods available in the literature to assess wheelchair sports fitness in a field-based environment, with special attention on outcome variables, validity and reliability issues, and non-physiological influences on performance. It also lays out the context of field-based testing by providing details about the Paralympic court sports and the impacts of a disability on sporting performance. Due to the limited availability of specialized equipment for testing wheelchair-dependent participants in the laboratory, the adoption of field-based testing has become the preferred option by team coaches of wheelchair athletes. An obvious advantage of field-based testing is that large groups of athletes can be tested in less time. Furthermore, athletes are tested in their natural environment (using their normal sports wheelchair set-up and floor surface), potentially making the results of such testing more relevant than laboratory testing. However, given that many tests, such as the multistage fitness test and the Yo-Yo intermittent test, have originally been developed for AB games players, the assumption that these can also be used for wheelchair athletes may be erroneous. With the array of AB aerobic and anaerobic field tests available, it is difficult to ascertain which ones may be best suited for wheelchair athletes. Therefore, new, wheelchair sport-specific tests have been proposed and validated. Careful selection of tests to enable coaches to distinguish between disability classifications, wheelchair proficiency and actual performance improvements is paramount as this will not only enhance the value of field-based testing, but also help with the development of meaningful normative data

Tests examining skill outcomes in sport: A systematic review of measurement properties and feasibility

BackgroundA high level of participant skill is influential in determining the outcome of many sports. Thus, tests assessing skill outcomes in sport are commonly used by coaches and researchers to estimate an athlete&rsquo;s ability level, to evaluate the effectiveness of interventions or for the purpose of talent identification.ObjectiveThe objective of this systematic review was to examine the methodological quality, measurement properties and feasibility characteristics of sporting skill outcome tests reported in the peer-reviewed literature.Data SourcesA search of both SPORTDiscus and MEDLINE databases was undertaken.Study SelectionStudies that examined tests of sporting skill outcomes were reviewed. Only studies that investigated measurement properties of the test (reliability or validity) were included. A total of 22 studies met the inclusion/exclusion criteria.Study Appraisal and Synthesis MethodsA customised checklist of assessment criteria, based on previous research, was utilised for the purpose of this review.ResultsA range of sports were the subject of the 22 studies included in this review, with considerations relating to methodological quality being generally well addressed by authors. A range of methods and statistical procedures were used by researchers to determine the measurement properties of their skill outcome tests. The majority (95 %) of the reviewed studies investigated test&ndash;retest reliability, and where relevant, inter and intra-rater reliability was also determined. Content validity was examined in 68 % of the studies, with most tests investigating multiple skill domains relevant to the sport. Only 18 % of studies assessed all three reviewed forms of validity (content, construct and criterion), with just 14 % investigating the predictive validity of the test. Test responsiveness was reported in only 9 % of studies, whilst feasibility received varying levels of attention.LimitationsIn organised sport, further tests may exist which have not been investigated in this review. This could be due to such tests firstly not being published in the peer-review literature and secondly, not having their measurement properties (i.e., reliability or validity) examined formally.ConclusionsOf the 22 studies included in this review, items relating to test methodological quality were, on the whole, well addressed. Test&ndash;retest reliability was determined in all but one of the reviewed studies, whilst most studies investigated at least two aspects of validity (i.e., content, construct or criterion-related validity). Few studies examined predictive validity or responsiveness. While feasibility was addressed in over half of the studies, practicality and test limitations were rarely addressed. Consideration of study quality, measurement properties and feasibility components assessed in this review can assist future researchers when developing or modifying tests of sporting skill outcomes.<br /